The FIRE simulations are used to address a wide array of questions in galaxy formation and intergalactic medium science, including the regulation of galaxy growth by stellar feedback, the properties of galactic inflows and outflows, the morphological transformation of galaxies, the quenching of star formation in massive galaxies and the need for active galactic nucleus feedback, the escape fraction of ionizing photons from galaxies, and the effects of stellar feedback on dark matter halos.